This application pertains to the art of light dimming circuits and more particularly to a three-way toggle dimmer switch combination using two independent toggle dimmer circuits for controlling the brightness of a lamp. In the past, many different types of electric circuits had been proposed for controlling the brightness of lamps or other lighting systems. At first, simple resistive load banks were used to absorb a portion of the voltage supplied to the lamp or lighting system application. This approach, however, is tremendously wasteful and inefficient.
Recent developments in solid state electronics have resulted in more efficient light dimming circuits. In particular, use of the silicon control rectifier (SCR) has become popular for this purpose. In an SCR, the conduction time of the current therethrough is controlled by varying the voltage applied to its gate terminal. It follows that this would allow the lamp or other lighting system to conduct for only a portion of a half-cycle, or a portion of the full cycle if the AC voltage was fully rectified.
Still further developments in the solid state electronics arts have lead to a triac device. A triac conducts during either half-cycle of standard AC line voltage depending upon the gate voltage applied to the triac. Traditionally, diacs have been used in combination with the triacs as triggering devices. As the names would imply, a triac is three terminal device whereas a diac is a two terminal device.
Basic electric circuits for controlling the brightness of lamps or lighting systems have been in existence for some time. However, a more complicated application is the three-way light dimming switch combination with independent dimmer circuits located in either switch, and with either switch having light dimming capabilities.
The prior U.S. Pat. No. 4,259,619 to Wall shows a fairly complex electromechanical apparatus having two separate light dimming circuits interconnected in a three-way light dimming switch combination. Each of the light dimmer switches has a common lead connected to a contactor arm. As a vertically actuated lever arm of either of the switches is moved from one limit of its vertical travel, a contact is broken. Also, as the vertically actuated lever arm moves to the opposite limit of its vertical movement, another contact is broken. As a result, the contactor arm of each dimming circuit requires two sets of contacts, one on each end, for proper circuit operation. Since the contactor arm is required to carry the full load current, the contacts and the arm itself must necessarily be ruggedized, and this requires a bulky and expensive structure.
An electronic dimmer circuit is interconnected between fixed contacts for the contactor arm in the prior arrangement disclosed by Wall for controlling the brightness of an associated lamp or lighting system. By proper connection of the fixed contacts of two light dimmer switches, and by using the common lead which connects to the actuator arm as the input and output, the intensity of a lamp can be varied from either light dimmer switch.
It has been found desirable to develop a new and improved three-way toggle dimmer switch and circuit which overcomes the above noted problems and others encountered with the prior art. The present invention meets these needs and others, and provides such a switch and circuit which is simple and easy to manufacture, efficient to operate, and less bulky than the prior devices.